1. Field of the Invention
The present invention relates to a technology for controlling a power supply in an image forming apparatus.
2. Description of the Related Art
It is known that, in an image forming apparatus, when loads of the image forming apparatus consume a large amount of power for activating the image forming apparatus, executing various processes such as a copy process, or the like, sufficient power cannot be supplied to the loads from only a commercial power source used as a main power source of the image forming apparatus. To overcome such a problem, there has been proposed a technology for compensating for lack of power supplied from the commercial power source by installing a capacitor as an auxiliary power source in the image forming apparatus such that power can be supplied from the capacitor to the loads when the loads consume a large amount of power. However, in the technology for compensating for the lack of the power supplied from the commercial power source by using the capacitor when the loads consume a large amount of power, the capacitor is frequently caused to charge and discharge, resulting in shortening a lifetime of the capacitor.
An image forming apparatus that includes a heating device having a measure against such a problem is disclosed in, for example, Japanese Patent Application Laid-open No. 2005-166633. Specifically, the heating device determines whether to use a capacitor based on an amount of power supplied from a commercial power source and a temperature of a heater heated by the power supplied from the commercial power source. More particularly, the heating device causes the capacitor to supply power for heating the heater only when the temperature of the heater is lower than a value while the largest amount of power for heating the heater is supplied from the commercial power source.
However, in the technology disclosed in Japanese Patent Application Laid-open No. 2005-166633, when the image forming apparatus is being warmed up, the temperature of the heater is often maintained lower than the value even when the largest amount of power for heating the heater is supplied from the commercial power source. Accordingly, the capacitor is often caused to supply power to the heater. Thus, when the image forming apparatus is activated or warmed up for recovering from an energy-saving mode or the like, the capacitor is almost always caused to supply power to the heater. Therefore, the number of times of charge and discharge of the capacitor increases, resulting in shortening the lifetime of the capacitor.